llvmpipe: Re-enable threading on windows.

src/gallium/drivers/llvmpipe/lp_screen.c

@@ -349,11 +349,6 @@ llvmpipe_create_screen(struct sw_winsys *winsys)
 
    lp_jit_screen_init(screen);
 
-#ifdef PIPE_OS_WINDOWS
-   /* Multithreading not supported on windows until conditions and barriers are
-    * properly implemented. */
-   screen->num_threads = 0;
-#else
 #ifdef PIPE_OS_EMBEDDED
    screen->num_threads = 0;
 #else
@@ -361,7 +356,6 @@ llvmpipe_create_screen(struct sw_winsys *winsys)
 #endif
    screen->num_threads = debug_get_num_option("LP_NUM_THREADS", screen->num_threads);
    screen->num_threads = MIN2(screen->num_threads, LP_MAX_THREADS);
-#endif
 
    util_format_s3tc_init();